1. Field of the Invention
The present invention relates to liquid level control apparatus and more particularly to controlling the liquid level within pressure vessels as used in the oil and gas industry, such as a gas scrubber.
2. Description of the Prior Art
Liquid level controls usually include a float located inside of a vessel in which the float has a connection by a shaft or an operating member, extending through the wall of the vessel, with a mechanism located exteriorily of the vessel which operates a liquid outlet or dump valve. In such an arrangement, the float movement with the rise and fall of the liquid level functions to open and close the outlet or dump valve thus maintaining a predetermined liquid level within the vessel. One of the problems of prior liquid level controls has been obtaining a positive "open" or "closed" control signal for a liquid drain or supply valve when a liquid float is disposed in a neutral position between a liquid level "high" or "low" position. This results in an arcing and burning of contacts, in an electric operated level control or a by-pass to atmosphere waste of gas pressure supply in a gas pressure operated liquid level control.
The most pertinent patent is believed U.S. Pat. No. 3,822,933 which discloses a housing threadedly inserted at one end through one wall of a vessel. The inward end of the housing is provided with a longitudinal cavity pivotally supporting an arm connected with a float raised and lowered by fluid in the vessel. The end of the arm opposite the float supports a magnet which magnetically attracts a second magnet upon downward movement of the float to pivot a second lever pivotally supported in a second cavity of the housing, parallel with the first cavity, to cover or uncover an orifice connected with a source of pressure. As the orifice is gradually closed by the lever in a throttling action the pressure source actuates a motor control valve for actuating a motor in turn controlling the input or output of vessel liquid.
The present invention solves the above problem and is distinctive over the prior art and the above patent by an unbalanced valve assembly biased "open" or "closed" in a snap action to respectively open or close a fluid outlet or dump valve in response to the rise and fall of a liquid level in a vessel.